Polycarbonate resins have excellent heat resistance, mechanical properties, and electrical properties, and they are widely used as materials in automobiles, in electric and electronic devices, in housing construction, and for manufacturing parts in other industrial fields. In particular, flame resistant polycarbonate resins are suitably used as parts in computers, notebook style personal computers, mobile telephones, and office automation and data devices such as printers, and copiers.
Blending a halogen-based flame retardant into a polycarbonate resin has been used in the past as means of imparting flame resistance to the polycarbonate resin. However, a polycarbonate resin composition comprising a halogen-based flame retardant that contains chlorine or bromine causes a decrease in thermal stability and corrosion of the molding machine screws and molds during the molding process. As an alternative method, a polycarbonate resin compositions comprising a phosphorus flame retardant are preferably used (for example, see Patent Documents 1 and 2).
The method of including such a phosphorus flame retardant in a polycarbonate resin can shorten the flaming time effectively through forming a char of a phosphorus compound on the surface of the resin and effectively diluting the combustible gases in the gas phase of combustion.
However, a polycarbonate resin that contains a phosphorous flame retardant causes a pronounced decrease in the impact resistance that is inherent in polycarbonate resins, so formulations that also include an elastomer are used. The applicant has made various proposals for such polycarbonate resins that contain both a phosphorus flame retardant and an elastomer as can be seen in Patent Documents 3 to 7.
More specifically, Patent Document 3 proposes a polycarbonate resin composition wherein the generation of white spot contamination on the molded surface is inhibited by blending a phosphorus flame retardant and a special anti-dripping agent comprising an organic polymer-coated polyfluoroethylene into an aromatic polycarbonate resin. Patent Document 4 proposes a polycarbonate resin composition prepared by blending a phosphorus flame retardant, polyfluoroethylene, and a polyorganosiloxane-containing graft copolymer, which is obtained by copolymerizing a first vinyl monomer and a second vinyl monomer with polyorganosiloxane at a specific ratio, into an aromatic polycarbonate resin. Moreover, Patent Document 5 proposes a polycarbonate resin composition prepared by blending a phosphorus flame retardant, a vinyl monomer-grafted silicone/acrylic rubber, and an anti-dripping agent into an aromatic polycarbonate resin at specific ratios.
Furthermore, Patent Document 6 proposes a polycarbonate resin composition prepared by blending talc as an essential component, a phosphorus flame retardant, a polyfluoroethylene, and a polyorganosiloxane-containing graft copolymer, which is obtained by copolymerizing a first and a second polyfunctional vinyl monomer at a specified ratio in the presence of a specified amount of polyorganosiloxane particles, into an aromatic polycarbonate resin at specific ratios. In addition, Patent Document 7 proposes a polycarbonate resin composition prepared by blending a phosphorus flame retardant, a fluoropolymer, a multilayered polymer having a crosslinked polyalkyl acrylate core and an alkyl (meth)acrylate polymeric shell, titanium oxide, carbon black, and a dye or pigment into a polycarbonate resin at specific ratios.